Earthquake in Crete

We just had a M = 6.0 earthquake in Crete. Here is the USGS web page for this earthquake.

This is an interesting region tectonically. The convergence of the Africa-India-Australia plates northwards towards the Eurasian plate runs from west of Europe, through the Middle East, through the Himalayas, out east towards the north side of Australia. As this large convergent plate boundary passes through these regions, it makes bends and these bends make the plate boundary have all the different types of faults (convergent, divergent, and strike-slip).

The plate boundary in the Crete-Greece-Turkey region is debated in the literature. There are different interpretations about what the faults are doing in this region. I will post a couple different maps below showing these different interpretations. (They probably are not all correct, but there may be tectonic “truths” in each of them.)

Here is a map that I put together that shows a simplified version of the plate boundary, showing one interpretation that favors some obliquity to the plate boundary on the eastern side of this map. I have placed the USGS moment tensor to show that this earthquake has a strike-slip sense of motion. I do not know which of the two fault plane solutions is correct, due to the wide range of different tectonic maps of this region. Before today, I did not know much about this area (just a general understanding of some of it). I love when these earthquakes happen because it gives me a change to learn about the different interpretations around the world…

I have placed the two options for the two fault plane solutions (right-lateral or left-lateral). Remember, when you are on one side of a strike-slip fault and you are looking across the fault to your friend, if they move to your right (and you move to their right, from their perspective), you are looking across a right-lateral (dextral) strike-slip fault. The obliquity of the plate boundary here is depicted as a right-lateral (oblique) plate boundary fault. Based upon this, I suspect that the fault is not the ~east-west striking left-lateral fault solution, but the ~north-south striking right-lateral fault solution. I may be wrong and someone who works in this area could correct me.

This is the USGS Intensity map that uses the Modified Mercalli Intensity Scale. It looks like this earthquake was felt across a broad region. Based upon the “Did You Feel It” map (composed of reports from real people, compared to this MMI map that is merely based upon a model), the MMI map is pretty good.

Here is a map that I found on the internets. It is from a Geological Society of America paper, but I cannot tell which (when I click on “take me to the page,” I get the log in page and it does not have any author information.) We can see their interpretation about how this plate boundary is more compressional on the west and transform on the east (at the Pliny and Strabo trenches). While there is conflict about the details, each map shares the sense of motion for the obliquity of the plate boundary here (right-lateral).

Here is another version from the Corith Rift Laboratory. This also shows right-lateral motion in this region.

Here is yet another map, also from a GSA paper. This one shows that there are a series of thrust faults, some with differing vergence (the direction that a thrust fault goes in when going from deep in the earth upwards to the surface). In my interpretation map above, the fault dips to the north, so is southward vergent.

Category(s): Chemeketa Community College, earthquake, education, europe, geology, HSU, plate tectonics, subduction, Transform

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